1. Field of the Invention
The present invention generally relates to equipment controllers, image forming apparatuses, and programs and, in particular, to an equipment controller having a CPU capable of switching to a low power mode when the equipment switches to an energy-saving mode, an image forming apparatus, and a program that controls the CPU.
2. Description of the Related Art
As image forming apparatuses such as printers, facsimile machines, copiers, plotters, and multi-task machines having plural such functions, ink jet recording apparatuses using a recording head that ejects, for example, ink liquid droplets are known. The image forming apparatus of this type ejects ink droplets onto a sheet during conveyance from the recording head to perform image formation (used synonymously with recording, printing, and imaging). Examples of the image forming apparatus include a serial-type image forming apparatus in which the recording head ejects liquid droplets to form an image while moving in a main scanning direction and a line-type image forming apparatus using a line-type head in which the recording head ejects liquid droplets to form an image without moving.
Note that in the present invention, the “image forming apparatus” refers to an apparatus that shoots ink droplets onto a medium such as paper, a thread, a fiber, a fabric, leather, metal, a plastic, glass, wood, and a ceramic so as to perform the image formation. Furthermore, the “image formation” refers to forming on the medium not only relevant images such as characters and graphics, but also irrelevant images such as random patterns (i.e., liquid droplets are just ejected and shot out). Furthermore, the “ink” is not limited to one as generally called ink, but it is used as a generic name of various liquid available for the image formation such as recording liquid, fixing treatment liquid, and liquid. Furthermore, the material of the “sheet” is not limited to paper. That is, the sheet refers to ones including an OHP sheet, a fabric, etc., onto which ink droplets are ejected, and it is used as a generic name of one including a medium to be recorded, a recording medium, a recording sheet, a recording paper, etc.
According to an information processing apparatus described in Patent Document 1, when display and music devices are controlled by plural tasks, the use or unused status of the devices is reported by the tasks. In consideration of the reported information and the execution statuses of the devices, optimum low power settings of the devices are calculated to attain energy saving. Furthermore, an information processing apparatus described in Patent Document 2 has a configuration for attaining the same object as the above.    Patent Document 1: JP-A-2005-182223    Patent Document 2: JP-A-2006-235907
According to the configuration of Patent Document 3, even if a printing apparatus such as a facsimile machine switches to an energy-saving mode, it is automatically restored from the energy-saving mode upon receiving data from the outside.    Patent Document 3: JP-A-2006-352914
In an embedded device (system) based on a real time OS, system time is managed. It is known that the embedded device is installed using a cyclic interrupt with a cycle timer. For example, when an image forming apparatus switches to the energy-saving mode to reduce consumption power, it stops supplying power to respective parts. For the processing of a CPU as well, there is no task (program) to be executed in the energy-saving mode. Therefore, the real time OS issues a WAIT instruction to switch to a mode (low power mode) that consumes less power.
However, in the switch to the low power mode by the CPU according to the WAIT instruction from the real time OS, a system timer is set at a predetermined cycle (for example, 1 msec). Therefore, even if there is no task (program) to be executed, a timer interrupt always occurs at a short cycle of 1 msec to cause the CPU to awaken. As a result, the low power mode cannot be appropriately executed at low power. In this case, if the cycle of the system timer is set to be long for attaining low power effects, the respective tasks (programs) cannot maintain hard real time property in general operations.